The present invention relates to a waterproof, wireless communication device.
There are known waterproof, wireless communication devices having a speaker for producing sounds. These devices include a grille on the front side of the speaker to protect the speaker. Once such a communication device is submerged in water, water infiltrates into the grille, thus muffling the sound produced by the speaker. In the case of e.g. a wireless communication device mounted on a ship, it may be splashed with water according to the location where it is installed, or water may infiltrate into the grille while the interior of the ship is being cleaned with water. In either case, the communication device may become unable to produce sound.
That is, if a large amount of rainwater or seawater infiltrates into the front grille, such rainwater or seawater forms a film on the grids of the grille due to surface tension of water, thus muffling the sound produced the speaker. Therefore, in order to reuse the communication device, it is necessary to discharge water by lightly applying impacts to the communication device or drying it.
In order to avoid this problem, Unexamined JP patent Application KOUKAI publication 2000-201388 proposes, as shown in FIG. 5, to apply electrical signals of a predetermined frequency to an amplifier 2 from a low-frequency oscillating circuit 1 to activate a speaker 3. With this arrangement, the sound pressure produced when the speaker 3 is activated is used to directly remove foreign matter that has infiltrated into the device through a grille 4, or a waterproof film (foreign matter blocking film) 5 provided inside the grille 4 is vibrated at a resonance frequency to remove water and other foreign matter.
But in the arrangement in which the sound pressure produced when the speaker is activated is used to directly remove foreign matter in the grille, when foreign matter is gradually removed and the amount of foreign matter remaining in the grille decreases, the sound pressure tends to be released through gaps formed as a result of removal of foreign matter. Thus, it becomes impossible to apply sufficient sound pressure to the remaining foreign matter, so that foreign matter cannot be removed completely.
In the arrangement in which the waterproof film is vibrated at a resonance frequency, while it is possible to vibrate the waterproof film at a low sound pressure, because the vibration conducted to air in the grille from the speaker is conducted to the waterproof film, and sounds conduct to outside through the waterproof film, large energy is lost until sounds conduct to outside, so that no sufficient sound pressure is produced. Thus, water and other foreign matter cannot be removed efficiently.